import sun.security.mscapi.CPublicKey;

class ListNode{
    public ListNode next;
    public int val;

    public ListNode(int val){
        this.val = val;
    }
}
public class MyLinkedList {
    public ListNode head;

    public void createList(){
        ListNode listNode1 = new ListNode(12);
        ListNode listNode2 = new ListNode(23);
        ListNode listNode3 = new ListNode(45);
        ListNode listNode4 = new ListNode(34);
        ListNode listNode5 = new ListNode(56);
        listNode1.next = listNode2;
        listNode2.next = listNode3;
        listNode3.next = listNode4;
        listNode4.next = listNode5;
        this.head = listNode1;

    }
    public void display(){
        ListNode cur = this.head;
        while (cur != null){
            System.out.print(cur.val + " ");
            cur = cur.next;

        }
        System.out.println();
    }

    public boolean contains(int key){
        ListNode cur = this.head;
        while (cur != null){
            if (cur.val == key){
                return true;
            }
            cur = cur.next;

        }
        return false;
    }

    public int size(){
        ListNode cur = this.head;
        int size = 0;
        while (cur != null){
            size++;
            cur = cur.next;

        }
        return size;

    }

    public void addFirst(int data){
        ListNode node = new ListNode(data);
        node.next = head;
        head = node;

    }

    public void addLast(int data){
        ListNode node = new ListNode(data);
        if (head == null){
            head = node;
        }else {
            ListNode cur = this.head;

            while (cur.next != null){
                cur = cur.next;

            }
            cur.next = node;
        }




    }

    public ListNode findIndex(int index){
        ListNode cur = new ListNode(index);
        while (cur != null){
            cur = cur.next;
            index--;
        }
        return cur;
    }

    public void addIndex(int index,int data){
        if (index < 0 || index > size()){
            System.out.println("不合法");
            return;
        }
        if (index == 0){
            addFirst(data);
            return;
        }
        if (index == size()){
            addLast(data);
            return;
        }
        ListNode node = new ListNode(data);
        ListNode cur = findIndex(index);
        node.next = cur.next;
        cur.next = node;

    }

    public void remove(int key){

    }
    public void clear(){

    }





}
